Process for recovering molybdenum



2,796,344 Patented June 18, 1957 PROCESS FOR RECOVERING MOLYBDENUM Joseph H. Brennan, NiagaraFalls, N. Y., assignon to Union Carbide and Carbon Corporation, a corporation of New York 1 No Drawing. Application Ma -10, 1954, Serial No. 428,802

4 Claims. (Cl. 75-121) This invention relates to the recovery of molybdenum from ore material containing sulfides of molybdenum.

Molybdenite concentrates may be more or less contaminated with sulfides of other metals, and when apure product is desired it is customary to roast such concentrates to oxide, extract the molybdenum with alkalis such as soda ash or ammonia, and recover the molybdenum as a molybdate.

In other instances, where a bulk sulfide concentrate consists, for example, principally of molybdenite (M082) and chalcopyrite (FeCuSz), the separation of these two sulfides by dilferential flotation results in the retention by the chalcopyrite fraction of varying quantities of molybdenite, and in the further refinement of this sulfide for the copper, and possibly silver values, the molybdenum is lost inasmuch as any of the known applicable methods would be economically prohibitive.

It is an object of this invention to provide a method for the recovery of molybdenum from molybdenite.

It is a further object of this invention to provide a method for the recovery of molybdenum from molybdenum-containing sulfide concentrates.

The method whereby these objects are achieved comprises oxidizing molybdenite to a water-solution molybdate by a self-propagating exothermic reaction with sodium nitrate and soda ash, leaching the reaction product and precipitating the molybdate from the leach liquid as calcium molybdate.

The oxidation of the sulfides by sodium nitrate and soda ash may be represented by the following reactions:

The ore is preferably comminuted to approximately 65 by D mesh size, the reagents may be standard, commercial-grade crystals. Sufiicient exothermicity is evolved during the reaction for almost complete conversion of the sulfide to sodium molybdate, thereby obviating the necessity for the prior roasting step as now practiced in the art. As shown above more than the stoichiometric quantity of the alkali metal nitrate and carbonate may be usefully employed in the oxidation of other sulfide minerals present to achieve a self-propagating reaction.

In the practice of the invention, the comminuted ore, sodium nitrate and soda ash are mixed together and placed in a suitable container that can be loosely covered during the reaction. The charge may be ignited either by heating the container and mix in a mutfie furnace to the initial reaction temperature (300 C. to 400 C.) or by cally heating with a torch or other suitable device. The ignited product is leached with water, and the sodium 2 molybdate is precipitated in a conventional manner as calcium molybdate.

Illustrative of the method of the invention, the following runs are listed:

Run N0. 1

Ten parts by weight of molybdenum-containing concentrate, reduced to 65 by D mesh size were mixed with 5.5 parts of sodium nitrate and 5.0 parts of soda ash.

The mixture was ignited, crushed and sampled. Analysis revealed a conversion of 91% to water-soluble molybdate, since, of the 4.14% available molybdenum 3.78% was recovered.

Run No. 2

Ten parts by weight of a mixture of chalcopyrite and molybdenite were mixed with 10 parts of sodium nitrate- (the quantity computed as necessary to oxidize the entire I sulfur content of chalcopyrite) and 5 parts of soda ash. The mixture was ignited, crushed and sampled. Analysis revealed a conversion of 99% to water-soluble molybdate.

Run No. 3

Ten parts by weight of molybdenum-copper concentrate from bulk molybdenite-chalcopyrite flotation process were mixed with 12.5 parts of sodium nitrate (an amount approximately 25% in excess of that required to oxidize all the sulfur) and 6 parts of soda ash (an amount approximately 50% in excess of that required to neutralize the oxidized sulfur). The mixture was ignited, crushed and sampled. Of the 750.8 grams of molybdenum available for conversion in the ignited product, 749 grams of water-soluble sodium molybdate were realized, indicating a recovery of 99.76%.

Run N0. 4

Ten parts by weight of molybdenum-containing copper concentrate were mixed with 8 parts of sodium nitrate and 3 parts of soda ash (the respective theoretical amounts for the oxidation of the molybdenite only). The mixture was ignited, crushed and sampled. Analysis revealed a conversion of 98.33% to water-soluble molybdate.

The foregoing runs serve to illustrate that the molybdenum in molybdenum-containing ores or concentrates may be successfully converted to a water-soluble molybdate in a one-step process with excellent recoveries of molybdenum.

A preferred method of converting the molybdenum in sulfur-containing molybdenum ore material to water-soluble molybdate according to the method of the invention is set forth as follows:

The molybdenum ore material is crushed to convenient size, sodium nitrate is added in at least a stoichiometric amount to oxidize all of the molybdenite plus the entire sulfur content of the molybdenum ore material; soda ash is added in double the stoichiometric amount required to neutralize the total sulfur oxidized and to supply additional sodium for the molybdate. The mixed charge is placed in a suitable container which may be provided with a loose cover, and is ignited by placing the container in a muffie furnace and heating to the reaction temperature (300 C. to 400 C.) or by locally heating with a torch or other suitable device. The ignited product is cooled, crushed, leached with water and the dissolved sodium molybdate is precipitated as calcium molybdate by a water solution of calcium chloride in a conventional manner.

What is claimed is:

1. A process for the recovery of molybdenum from ore material containing sulfides of molybdenum which process comprises mixing said ore material with an alkali metal nitrate in a stoichiometric amount necessary to oxidize I said sulfides of molybdenum; adding an alkali metal carbonate in a stoichiometric amount necessary to neutralize the total sulfur oxidized; heating said mixture to its reaction temperature thereby converting said sulfides of molybdenum to an alkali metal molybdate; leaching the reaction product with water; recoveringthe dissolved molybdate 2. A process 'for the recovery of molybdenum from ore material containing sulfides of molybdenum which process comprises comminuting said ore material; forming an admixture of said: ore material and at least a stoichiometric amount of an alkali metal nitrate, and at least astoichiometric, amount of an alkali metal carbon ate based on the amount of said sulfides; reacting said admixture, exothermically; leaching the reacted product with water; recoveringthe molybdenum values from the 15 leach liquor.

3. A process for the recovery of molybdenum from ore material containing sulfidesof molybdenum which process comprises comminuting said ore material; forming an admixture of said ore material and at least a stoichiometric amount of sodium nitrate, and at least a stoichiometric amount of soda ash relative to said sulfides; reacting said admixture exothermically; leaching the reacted product with water; recovering the molybdenum values from the leach liquor.

4. A single-step process for converting the molybdenum values of ore material containing sulfides of molybdenum to a water-soluble molybdate which process comprises reacting a mixture of said material, and at least stoichiometric amounts based on the amount of said sulfides of molybdenum of an alkali metal; nitrate and an alkali metal carbonate.

References Cited in the tile of this patent UNITED STATES PATENTS 787,758 Herrenschmidt Apr. 18, 1905 2,435,304 Foerster et al. Feb. 3, 1948 FOREIGN PATENTS 14,644 France Nov. 11, 1911 (Addition to No. 412,641) 21,891 Norway Dec. 4, 1911 112,417 Australia Ian. 28, 1941 OTHER REFERENCES Handbook of Nonferrous Metallurgy, Recovery of Metals, by Liddel. Pub. 1945 by McGraw-Hill Book Co., Inc., page 636. 

2. A PROCESS FOR THE RECOVERY OF MOLYBDENUM FROM ORE MATERIAL CONTAINING SULFIDES OF MOLYBDENUM WHICH PROCESS COMPRISES COMMUNINUTING SAID ORE MATERIAL; FORMING AN ADMIXTURE OF SAID ORE MATERIAL AND AT LEAST A STOICHIOMETRIC AMOUNT OF AN ALKALI NITRATE, AND AT LEAST A STOICHIOMETRIC AMOUNT OF ANA ALKALI METAL CARBONATE BASED ON THE AMOUNT OF SAID SULFIDES; REACTING SAID ADMIXTURE EXOTHERMICALLY; LEACHING THE REACTED PRODUCT WITH WATER; RECOVERING THE MOLYBDENUM VALUES FROM THE LEACH LIQUOR. 